Lever train actuator



Oct. 28, 1969 ZENZEHUS 3,474,687

LEVER TRAIN ACTUATOR Filed Feb. 23, 1968 2 Sheets-Sheet 1 o 46 FIG.

' e. E. ZENZEFILIS INVENTOR avg (Z6 ATTORNE v Oct. 28, 1969 G. E. ZENZEFILIS LEVER TRAIN ACTUATOR 2 Sheets-Sheet 2 Filed Feb. 23. 1968 E a E GEORGE E. ZENZEFILIS INVE OR wan? TTORN United States Patent Int. Cl. G05g 1/00 U.S. Cl. 74518 9 Claims ABSTRACT OF THE DISCLOSURE A chain of connected levers are pivoted by individual solenoids connected to each lever, to give rise to a wide range of very precise increments of movement in the end lever of the chain. Any one lever movement results in a fractional movement of the end lever in the chain. The levers of the chain are devoid of pivots and other pins and instead are formed from a continuous sheet of material with the connecting strands being sufiiciently reduced in dimension to act as fiexure joints. The lever chain is restrained to movement in the plane of its sheet by a pair of spaced plates disposed one on each side. The lever train or chain moves a reader mechanism for retrieving information recorded in very compact form, for example in the memory storage of computers.

This invention relates to moving and controlling precisely the motion of a light load, for example an electromagnetic or optical reader of compactly stored information such as the memory bank of computers. More specifically it relates to a connected chain of levers each individually pivoted by a separate power unit to achieve this result wherein flexure joints are used instead of pin pivots and pin and link connectors. In many fields, but especially in the field of computer operations, data are stored on rectangular cards or on cylindrical drums or on circular discs, in the form of arrays forming tracks, to which access must be had-for the use of the information which they carry. In order for the information to be extracted at all, the transducer or reader, which is the means for linking the information contained in the aforementioned configurations and the outside world, must be aligned precisely 'with the track. Very often for economic purposes, one transducer services several tracks, and in these cases during the course of operations it must move from its previous track location to the desired new track location, and it must perform this motion rapidly and precisely in order to keep pace with the unusually fast processing speeds of electronic information handling.

The power input to the prime mover is a function of the load inertia, the speed with which it has to move, and the interval it has to cover from its previous location to its new one. Additionally, the required power is a function of the frictional forces involved, the accelerations and decelerations due to the unavoidable vibrations of the machine, and the forces, in general, that the transducer and reader must resist while in position. Also, because of the quite rapid motion rates involved, the wear on all moving parts is very often significant, and after a time they must be replaced.

It is an object of this invention to provide an actuating mechanism for a transducer having a minimum number of moving parts a minimum of inertia or mass, and a minimum of play, or mechanical hysteresis, involved, combined with a large degree of precision and also combined with low-cost of fabrication.

It is an additional object of this invention to provide a configuration of prime movers which both occupies a very small space and also has a geometry ideally suited for stacking; that is, combining a plurality of such prime movers with a number of discs, or drums, or cards, in

one system forming a large capacity of data storage and retrieving in a small space.

A further object of this invention is to provide a means of effecting the motion of the transducer or reader from its initial position to any of a number of pre-determined locations where desired information is recorded, upon the basis of their address alone, and without having to have previous knowledge of the exact track radius in the case of discs, or track axial position in the case of drums, or track coordinates in the case of cards, in any given configuration. Prime movers of the class which can accomplish this type of final position selection are generally known as random access digital prime movers, and have the ability to jump, so to speak, from one location to another without any consideration of the intervening locations. Evidently, a prime mover which need not refer to the specifics of the path but only requires to know the end of the path, and which need not even require a knowledge of the origin of the path, is inherently more useful and practical than one which must seek out these factors. Furthermore, such a prime mover is adaptable for use with interchangeable discs, or drums, or cards.

Other objects, advantages and features of the invention will be apparent in the following description and claims considered together with the drawings forming an integral part of this specification in which:

FIG. 1 is a plan view of a presently preferred embodiment of the invention with parts of the upper plate broken away to show the internal construction.

FIG. 2 is a three dimensional view of the belt and drum mechanism of FIG. 1 for rotating the crank arm.

FIG. 3 is a plan view on an enlarged scale of the lower end of FIG. 1.

FIG. 4 is an end view of the mechanism of FIGS. 1 and 3 but one the scale of FIG. 3.

Referring to the drawings, the purpose of the mechanism is to move a transducer or reader 43 across a disk 70 upon which is recorded at discrete radial positions forming circular tracks, various types of information. Such discs may record their information in a number of different ways, for example, by magnetizing material on the surface or in the body of the disk or by photographically recording the material on the disc. The reader 43 accordingly, picks up this information electromagnetically in the case of magnetizable disks and optically in the case of photographically recorded data. The transducer or reader 43 is mounted on a carriage 71 which slides on a. pair of rods 44 and 45. This carriage is moved backwards and forwards on the rods by means of a connecting rod 42 which is pin jointed at 47 to the carriage 71 and pin jointed on its other end at 46 to a crank arm 41 which in the present configuration or embodiment magnifies the movements of the lever train. The magnifying crank arm 41 is pivoted at 72 to a drum 40 about which is wrapped a flexible wire or ribbon or belt 39 tensioned by a spring 73. The purpose of the lever chain (to be described) is to pull on the ribbon 39 or relax the pull on the ribbon 39 by very precise amounts, whereupon the spring 73 either yields or takes up the slack to cause the drum 40 to rotate. This in turn magnifies the amount of movement of the ribbon 39 because of the length of the crank arm 41, and the motion of its tip is imparted to the carriage 71 by the connecting rod 42.

Referring particularly to FIG. 2 there is illustrated the structure whereby the ribbon or belt 39 is wrapped completely around the drum 40 while maintaining the pull in a plane. The belt 39 has one end reduced in width as at and a more central part is apertured with a lengthwise slot '86. The end 85 is wrapped around the wheel 40 and passed through the aperture 86 and hence to the spring 73.

The motive force for moving the ribbon 39 is supplied by a plurality of solenoids 50* through 55, and their motion when energized is supplied through a corresponding number of free floating levers 27 through 32, having one end connected to each of the solenoids by means of conplers 62 through 67. These levers and solenoids can be disposed in any suitable array, and a straight line array is illustrated. The levers are all connected together in a train or chain, and this lever chain is provided particularly in accordance with the invention. Each lever and its connecting link to each solenoid and its connecting link to an anchor spring are all formed of a continuous single sheet of material, preferably metal. The levers and flexure joints thus form a single, continuous, unitary structure. While this entire lever system could be punched out of sheet metal or other sheet material, it is inexpensively formed by photochemical etching, or may be formed by other suitable process, such as electrochemical etching, or mechanical milling. The photochemical etching or milling has the added advantage of preserving the temper or hardness of the material uniformly, and at the same time does not introduce any burrs, or unwanted sharp bends or deformations, which might interfere in the motion of the sheet and containing plates 48 and 49, the latter being at close proximity with the sheet.

Referring now to the lever chain 27 through 32, each lever has a corresponding end connected to its respective solenoid 50 through 55 by means of flexure joints 8 through 13, which terminate at their other ends in a plurality of enlarged mounting plates 2 through 7, which can be of any desired shape or size and a round configuration is illustrated. A plurality of fasteners, such as flat headed screws, secure these mounting plates to coupling pieces 62 through 67 connecting the said mounting plates to the solenoid plungers or armatures 56 through 61 of the associated solenoids 50 through 53. These coupling pieces are used merely for the particular commercially available solenoids illustrated.

The other ends of levers 27 through 32 are connected through flexure joints 74 through 79 to integrally formed spiral springs 33 through 38. The lever 27 farthest from the load has this spring secured end held stationary in space but freely pivotable by means of an integral solid anchor 1 secured to a base plate 48. A pair of flexure joints 14 and 21 extend from the anchor plate 56 to the left end of lever 27 as seen in FIG. 1. The left ends of all of the other levers are connected to the mid point of the next preceding lever by a pair of flexure joints, flexure joints 15 through being located immediately adjacent the mid point of the lever and fiexure joints 22 through 26 being immediately adjacent the left end of the next succeeding lever in the chain or train. By using levers of bent shape, the three fiexure or connecting joints for each lever may be in a straight line and the solenoid pull is at right angles to this line.

The thickness of the original sheet of material from which the entire lever train and associated springs and flex-ure joints, etc., are formed is preferably of a thickness larger than that of the smallest width of each fiexure joint. This relationship prevents buckling during stressing of the levers by the movement of their ends connected to the energized solenoids, or the movement of their other end connected to the preceding levers when the latter are acted upon. Buckling or instability is undesirable as it increases friction by rubbing on plates 48 and 49. However, the actual thickness is not important, inasmuch as a number of these identically formed lever trains may be stacked one on top of the other to obtain any desired stability or strength factor. The material from which the entire lever assembly is formed depends upon the desired strength factor for each assembly and steel or other metals may be used. Furthermore, other non-metal sheet materials of a homogeneous structure, such as sheet plastic, could be used.

In actual practice, lever systems have been successfully made from single sheets of beryllium copper and from stainless steel. The stainless steel employed was A181 302 Full Hard. Both types of sheets were simply formed by photographically projecting a drawing of the system on a sensitized surface on the metal and etching through the metal. Sheet thickness was ten thousandths of an inch and width at fiexure joints was twenty thousandths. These lever chains were all in tension systems. For compression lever systems or combination tension-compression systems, the flexure width could be sheet thickness for single sheet systems but, of course, stacking of identical systems can be employed in compression also, especially when the stacked lever chains are adhered together. When forming the single piece lever chain, a spacer can be cut from the same material, and shim stock or other thin sheets similarly formed added to it to obtain clearance between the guide plates 48 and 49. Shims of three thousandths added to the top and bottom of the spacer provided satisfactory working clearance. The guide plates 48 and 49 are preferably of hard material and aluminum sheets are satisfactory if they are anodized sufliciently thickly to be known as anodized hard. The levers may have an outline greater than required for beam stresses to assist in stabilizing the chain between the plates.

Considering now the geometry of the lever train 27 through 32, it will be noted that the three flexure joints of each lever are in line. This creates a simple balance beam lever chain and produces a displacement at the middle of each lever equal to one half of the displacement of its outer flexural joints 8 through 13 because of the selective actuation of one or more of the solenoids 50 through 55. Solenoid 55 is shown in its actuated position and it produces a displacement at the middle of lever 32 that is one-half of the solenoid movement. (The reading head 43 correspondingly is situated at the mid point of its range.) If solenoid 54 is actuated the center of its associated lever 31 moves one-half of the solenoid distance, and this lifts the outer end of lever 54 one-half of the solenoid movement, but this movement in turn, is reduced oy one-half as it is received by the center flexural joint 20 of lever 32. The total movement at flexure joint 20 therefore, because of actuation of solenoids 55 and 54, is one-half of the solenoid movement of 55 plus one-fourth of the movement of solenoid 54. Going up the chain, actuation of solenoid 53 will produce one-eighth of its movement at flexure joint 20 and so forth upon the chain. The total displacement, therefore, of the flexure joint 20, and consequently of the ribbon or wire 39 is shown by the following equation:

In this expression the designation for the solenoids 55 through 50 is in the usual Boolean algebra sense, that is, they can have a value of either 0 to 1, which means that their respective solenoids are either acting or not acting. In this fashion the motion of the wire or belt 39 is of a quantized nature and can have any of 64- values, each being an increment of one sixty-fourth of the movement of a solenoid plunger. The range of movement therefore of the belt 39 is approximately double the motion imparted to lever 32 by its solenoid 55 at the solenoid end.

Any number of levers can be formed in the chain and the added levers multiply the increments of motion by 2. For example, a six lever train has resulted in a reader travel of 3.175 inches of 64 positions of 0.050 inch interval. A seven lever train of the same total travel gives 128 positions of 0.025 inch interval.

An obvious advantage of this type of lever chain actuator is the fact that several sheets of the photochemically etched material can be superimposed on one another to accommodate a reasonable range of loads. Another advantage is the fact that there is no wear at all in the principal parts of the mechanism, since the levers by design always flex within their elastic region at a stress well within their endurance limit. A further advantage is in the fact that there is no hysteresis or mechanical lost motion in the flexing parts because there are no pivot pins and consequently no wear. A still further advantage of the present configuration is the fact that the aforementioned plates permit efiicient action even though the flexural material is thin and slender, because they act similarly to the guide of a Bowden cable. An additional advantage is the facility with which the number of steps can be increased, always by a factor or two, simply adding another lever to the chain of the fiexure sheet. A feature of all of these levers, fiexural joints, and springs, is that they are all formed continuously and without any pivots, and without any sliding action, from a single sheet of material contained between two flat plates which restrict all motions and tendencies to buckle, except planar motions.

Referring now to the crank arm 41 and the connecting rod 42, it will be noted that the pivot joint between the two at 46 moves in a circular path that does not touch the path of travel of the carriage pin 47. The projection of the path of travel of pin 47 is designated by 69 and a tangent to the circular path parallel to 69 is designated as 68 and the offset or distance between them is designated by 84. This oifset 84 is carefully calculated to give a very precise motion magnification of the linear type of motion derived from the lever chain 27 through 32. If linear motion is transmitted to this rotary motion device without careful calculation, the increments of carriage motion would be unequal to the circular motion. In practice a computer is used to search out the most favorable combinations. This precision is obtained by a combination of two errors that are naturally inherent in the crank arm 41 mechanism and the ofiset 84. The projected length of the connecting rod 42, that is, the distance between the pin 46 and the pin 47, measured transversely across the path of travel of the transducer 43 is continually changing as the lever 41 rotates. The precision becomes a matter of optimizing the three parameters of the length of crank arm 41, the length of connecting rod 42 and the ofiset 84, for a selected are of arm rotation. For an arc of swing of arm 41 of about 30 the error has been reduced to .03 of one percent.

Referring now to FIG. 4, it will be noted that the guide plates 48 and 49 are recessed at 80 at the region of the solenoid fiexure mounts 2 through 7. These recesses 80 are to accommodate the solenoid coupler to the solenoid plunger 56 by means of a retaining pin 83, and to accommodate also the heads of the screws by which the flexure mounting plate 7 is fastened to the solenoid coupler 67. Formed in coupler 67 and in mounting plate 7 is a slot 82 through which a stationary stop pin '81 passes, and this pin is tightly secured in bores passing through both guide plates 48 and 49. In addition to acting as a stop pin to limit motion of movement of the solenoid plunger, pin 81 also acts as a guide pin to channel the pulling solenoid force on the lever ends parallel to the fiexure joints between levers. The contact between this pin 81 and the ends of slot 82 constitute the only possibility of wear in the entire lever chain system. This wear possibility is reduced because the contact is an abutting contact and not subject to as much wear as a rotating contact.

Considering now the spiral springs 3338 shown in FIG. 1, theoretically these could be eliminated in a tension lever chain, as illustrated, because the loading spring 73 imposes tension on the levers to return them to a rest position. However, on a 6 lever chain this force is reduced to one sixty-fourth, on a 7 lever chain to oneone hundredth and twenty eight and correspondingly in an eight lever chain. The force becomes so weak that as a practical matter springs are required and the integrally formed springs and flexure joints are inexpensively provided. These springs also act on the solenoid of the lever next up stream in the chain to return the solenoid armature to its rest position.

Return spring solenoids could be directly connected to the levers to give rise to a spring return force in lieu of or in addition to the spiral springs 33-38. When the system lifts a load against gravity a lever spring may not be needed.

Considering now the switching for actuating the so lenoids 50-55, this is so conventional that it is not shown. A keyboard can be provided with a key for each position that is preconnected to the desired solenoids 50-55 that will produce movement of the head 43 to the selected station. Alternatively the position can be dialed or switches otherwise actuated.

Regarding the take up spring 73 for the compound belt 39 and 85, it will be appreciated by those skilled in the art that this system does not permit inertia-caused overrunning when the speed or frequency of operation is fast. This same result could be obtained in other ways. The belt or wire 39 would be tightly tensioned and moved with no possibility or overrunning.

The invention has been described with reference to a presently preferred embodiment as required by the rules. It will be apparent to those skilled in the art that various modifications can be made in the light of the disclosure. For example, the connecting flexure joint need not be to the mid point of the lever, and different solenoids could cause different amounts of movement to the associated levers.

There is included within the language of the following claims all such variations and modifications that come within the true spirit and scope of the invention.

I claim:

1. An actuating mechanism for moving an object precisely to a selected one of a plurality of precisely located stations comprising:

(a) a plurality of arrayed levers each having three connecting points, one at each end and at an intermediate point;

(b) flexure joints connecting the intermediate point of one lever to one end of an adjacent lever to form a lever chain;

(c) individual prime mover for each lever for moving the other end in a direction generally parallel to the direction of pull on the lever-to-lever flexure points;

(d) means pivoting said one end of the lever on one end of the chain;

(c) means for connecting the object to an intermediate point on the lever on the other end of the chain; and

(f) means for selectively energizing the prime movers to cause said object to be moved to a selected station in its range of movement.

2. An actuating mechanism described in claim 1 wherein the levers and the flexu-re joints form a unitary mechanical structure.

3. An actuating mechanism described in claim 1 wherein the levers and flexure joints are formed from a single sheet of material and constitute a continuous unitary mechanical structure.

4. An actuating mechanism described in claim 1 wherein the levers and flexure joints are confined to movement in a plane by a pair of plates spaced one on each side of the levers and flexure joints.

5. An actuating mechanism as described in claim 3 wherein a plurality of lever chains are stacked one on top of the other to achieve a desired strength of chain.

6. An actuating mechanism as described in claim 3 wherein a spring is integrally formed from the same sheet of material and is integrally connected to a lever to return the lever to a rest position.

7. An actuating mechanism as described in claim 3 wherein the prime movers are connected to the levers through a fleXure joint formed from the sheet.

8. An actuating mechanism as defined in claim 1 wherein the levers and flexure joints are formed from a single sheet of material; the chain is disposed between a pair of spaced plates for guidance; and the levers have a transverse dimension Parallel to the plates that is in excess of stress requirements to assist in guidance by the plates.

9. The combination of the actuating mechanism of claim 1 and a movement multiplying mechanism connected between the lever chain and the object comprising:

(a) a drum having a periphery and a drum axis;

(b) a crank arm pivoted on the drum and having an outer end;

(c) means defining a linear path of movement having an axis for moving the object;

(d) a connecting rod between the object and the outer end of the crank arm; and

References Cited UNITED STATES PATENTS 1,091,602 3/1914 Tompkins 74-516 2,917,943 12/ 1959 Vlannes.

2,946,236 7/ 1960 Joseph 74-480 3,399,392 8/ 1968 Funazuka.

FRED C. MATTERN, JR., Primary Examiner 20 F. D. SHOEMAKER, Assistant Examiner US. Cl. X.R. 

